David Hearn and Scott Parel are tied for second place at 7-under-par 65 at Pete Dye Golf Club.
There was a one-hour fog delay to start the opening round and it led to play being suspended due to darkness. Fourteen players will return to the course Friday morning at 8:00 a.m. (ET).
McLachlin is a member of the PGA TOUR, but did not qualify for the FedExCup playoffs, which started this week. He is 156th on the money list and will need a big end of the year at the Fall Finish.
But for this week he is on the Nationwide Tour, trying to get a win.
'It is a nice change to think about winning instead of trying to make cuts and about moving up the money list,' said McLachlin, who has made 10 cuts in 21 starts this year on the PGA TOUR.
He started with three consecutive pars on Thursday, then holed a pair of 30- foot birdie putts at four and five. He made it three in a row thanks to a 5-footer at the par-5 sixth.
McLachlin collected his last birdie on the opening nine with a tap-in effort at the eighth.
On the second nine, McLachlin looked to be in great shape at the par-four 11th. He missed a 5-foot birdie putt, but drained a 15-footer for birdie at 12.
He knocked his third shot to 5 feet to set up birdie at the par-5 14th. McLachlin rolled home a 15-foot birdie putt at the 15th to get to 7-under par for the championship.
McLachlin finished off his round in style. At the par-5 17th, he two-putted from 12 feet for a birdie and made yet another 30-footer for birdie at the last to miss D.A. Points' 2004 course record by just a shot.
'I hit the ball well, put it on the greens and made the putts,' said McLachlin, a two-time runner-up in his Nationwide Tour career. 'It seemed so easy.'
Brian Smock is 6-under par through 17 holes.
Kyle Thompson, Kevin Gessino-Kraft and Ian Leggatt are knotted in fifth place at 5-under 67.
Defending champion Jason Enloe, Todd Demsey, Brad Ott, Jimmy Walker, Matthew Jones, Tom Carter and Chad Collins are in the clubhouse at 4-under 68, while Lee Williams is 4-under with one hole to play.